687218021 has 8 divisors (see below), whose sum is σ = 785550720. Its totient is φ = 588925008.

The previous prime is 687218003. The next prime is 687218027. The reversal of 687218021 is 120812786.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 687218021 - 2¹⁰ = 687216997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687218027) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61175 + ... + 71531.

It is an arithmetic number, because the mean of its divisors is an integer number (98193840).

Almost surely, 2^687218021 is an apocalyptic number.

It is an amenable number.

687218021 is a deficient number, since it is larger than the sum of its proper divisors (98332699).

687218021 is a wasteful number, since it uses less digits than its factorization.

687218021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19843.

The product of its (nonzero) digits is 10752, while the sum is 35.

The square root of 687218021 is about 26214.8435242326. The cubic root of 687218021 is about 882.4664025922.

The spelling of 687218021 in words is "six hundred eighty-seven million, two hundred eighteen thousand, twenty-one".